TACSAT 4 is a U.S. Navy satellite flying in a unique, gravitationally-stable orbit ranging from 400 miles (644 km) high to more than 7,300 miles (11,748 km) in altitude. From that orbit, the craft's UHF communications package will connect military units via radio. The satellite was developed under the auspices of the military's Operationally Responsive Space office, which was chartered to investigate and fly less costly niche missions designed to serve tactical needs. TacSat 4 flies three times closer to Earth than traditional military communications satellites, meaning users on the ground have nine times the signal strength compared to legacy systems in higher orbits.